Seeking Comments on New Date Line Theory

[James G. Stoveken]

I've been pretty much at a loss trying to follow this whole sextant/navigation issue.  Chris's post is very straight-forward and understandable.  I plan to go back through this discussion and see if it makes more sense to me now.  Thank you, Sir!

[Chris Johnson]

Mrs.L.Smith , By recomputing the 0720 radioed fixed position near Nukumanu island(s) , proof comes up that the great circle route seen in many maps , books and internet sites does not at all apply to the July 2nd flight. And it has been published : European Journal of Navigation , vol. 9 , no.1 , april 2011 : "Frederick Noonan Precomputed  a Running Sunset Fix for Amelia Earhart´s Flight from New Guinea to Howland , July 2 , 1937".

I would be very interested in reading the article you cite (in the European Journal of Navigation , vol. 9 , no.1 , April 2011).  Do you have a link to it in English? Or I could translate it if necessary.  Thanks.
Rick J

These may be what h.a.c. van asten is quoting: 2 pdf files authored by h.a.c. van asten published in the European Journal of Navigation. It may help if this thread is still valid :)

[Martin X. Moleski, SJ]

These may be what h.a.c. van asten is quoting: 2 pdf files authored by h.a.c. van asten published in the European Journal of Navigation. It may help if this thread is still valid :)

Nice work, Chris--most helpful.  Thanks!

Comments on the first article.

"While Noonan most probably used his Pioneer marine sextant to fix his position on the roads of Howland when flying at 1,000 feet altitude, with the sun in mean time whereas the true sun should be taken, it was, as we will presently see, this combination, although not being the flight's laesio enormis, that triggered the primary impulse to not sighting the island before the fuel ran out. Both theory and practice became antagonistic to safety because the bubble sextant has its reference line which is the artificial horizon, over sun's centre and the marine sextant at sunrise registers on the optical sun's upper limb in the horizon, since due to severe refractive distortion the lower limb falls into disuse" ("Where to Search for the Earhart Lockheed Electra").

Some questions:

• Did Noonan have a "Pioneer marine sextant" on the flight?  How do we know that he did?  In other words, what contemporaneous sources are there that back up this assertion?
• What evidence is there that the sun sight was taken at 1000'?
• What evidence is there that Noonan used "mean time" rather than "true time"?
• What evidence is there that Noonan's marine sextant was not equipped with a bubble to provide an artificial horizon?  If he did have a marine sextant modified to be used in flight, how might that affect this argument?
• How do we know that Noonan used only one observation with one instrument?  Doesn't the concept of a "preventer" (a second instrument carried to check errors in the use of the primary instrument) suggest using both instruments to check the validity of an observation?

This is a keeper: "When opening a can of worms there is one way only to get them in again: take a greater can (this being Zimurgi's First Law of Evolving System Dynamics)."

And this: "navigators do in the long run not get lost: they go astray for a restricted period of time."

The conclusion of the article is in the final figure: they splashed and sank in a region roughly 85 miles north-northwest of Howland.

Comments on the second article.

"Whatever algorithm is followed, be it H.O.208, any logarithmic gonio table, or e.g. the Douwes-Borda formula, the here recomputed endogenous outcomes remain constant: the Earhart to Herald Tribune Offices, New York, June 30, 1937 cable, reading in part: "..In addition FN has been unable [electric breakdown at Malabar radio station. auth.] account radio difficulties to set his chronometers lack knowledge their fastness or slowness.." later outdated since the 071930 GMT, 0720 by radio communicated time-coordinates group is inviolably interconnected by mathematical precomputation with heliographic time as exogenous parameter which made a structural time error impossible: the on board chronometers [and Longines hack watch] must have been perfectly synchronous with a record of the Greenwich time and for that matter: a navigator would never reset two [of three] chronometers on his own initiative, knowing thereby activating Spode´s Law [3] in its deadly configuration" ("Frederick Noonan Precomputed a Running Sunset Fix for Amelia Earhart's Flight from New Guinea to Howland, July 2, 1937").

That is one long sentence.  It has many component parts.  But it hinges on the claim that Noon did not get an accurate time check before leaving Lae.  The evidence is from a telegram on June 30, 1937.  Although this was one of the contributing factors in their failure to depart on June 30, that particular problem was rectified by two independent time checks on July 1 and July 2.  All of the computations that flow from misunderstanding of the historical record may be perfectly correct, but they are irrelevant because they are based on a faulty assumption.

[h.a.c. van asten]

Moles. Comment 2nd article. The ´long sentence´ says that Noonan , after having no time check initially , must before take off have acquired a good record of the Greenwich time , since the 071930 /0720 GMT established position is connected to latitude , longitude and time for sunset , these figures being inviolably interconnected by spherics algebra , so that an erroneous chronometer setting o/b of A/c was impossible (there has formerly been rumour that a watch time error was the basis of breakdown).

[h.a.c. van asten]

Molsk. 1. Noonan carrie most probably an A-5 Pioneer instrument. 2. For a sharp view of the local horizon it was necessary to fly as low as possible , for altitudes higher than 3,000 ft the horizon is invisible due haze , the world over. 3. The 071930 GMT sunset fix approves , together with radio messages @ GMT hours , that A/c was flown on GMT schedule . "True" , local and other schedules were impractical if not impossible. 4. Any sextant configuration would not have influence on astro observations and reductions. 5. No. One instrument at a time : checking instruments against each other not needed due to calibrations. A "preventer" was in this case a marine sextant for special observations , like on the local horizon. A marine sextant has greater accuracy (no trembling bubble) than artificial horizon configuration.

[Mona Kendrick]

If a "preventer" is used for special observations, and not as a backup to the octant, what is it that the preventer prevents?  I'm not being flip.  I'm just trying to understand the terminology.

LTM,
Mona

[h.a.c. van asten]

M.Kendr.The word "preventer" has been used for a marine sextant , having been on board of Clipper aircraft besides the bubble sextant. The marine sextant could be used for observations at low altitude with the local horizon traced sharply ; generally the mar.sext. has better accuracy  (no trembling bubble) than the bubble specimen. Before becoming an air navigator , Noonan made a long career at sea ; he was licensed "All Oceans" and it is probably therefore he had great confidence in the marine sextant.

[Walter Runck]

If a "preventer" is used for special observations, and not as a backup to the octant, what is it that the preventer prevents?  I'm not being flip.  I'm just trying to understand the terminology.

LTM,
Mona

I think the consensus on terminology is that FN used "preventer" to mean backup or secondary unit.  The primary unit was the Pioneer bubble octant, a device designed for aviation use with a built-in artificial horizon, so all you had to be able to do was correctly identify a star, see it and take a sight (no view of the natural horizon needed).  The secondary or "preventer" was a marine sextant that had been designed and built (by Brandis) to be used on a ship with the natural horizon.  This unit was later modified (google "Byrd sextant" for an example) with a homemade artificial horizon consisting of a spirit level and a small lens. My belief is that this lens is the "inverting eyepiece" Gallagher reported finding.

Hindsight allows for all kinds of theoretical suppositions and bloviation on what FN would have done or what someone armed a priori with the knowledge that the flight was not going to be supported by ADF could do simply because those things are possible, but there is no contemporary evidence of intent to do anything other that what had previously been done: use celestially augmented DR to get within range of the radio transmitters on or near Howland and ride the beam in.

I doubt the "preventer" ever came out of the box until they landed.

[Mona Kendrick]

Let me try re-phrasing my question: why did Fred call his marine sextant a "preventer"?

Mona

[Walter Runck]

Let me try re-phrasing my question: why did Fred call his marine sextant a "preventer"?

Mona

To prevent getting lost if there was a problem with his primary celestial navigation tool, the Pioneer octant. 

Preventer is also a sailing term for a piece of safety gear.  FN went to sea in the days of sail and probably had a pretty solid nautical vocabulary.  That's where a lot of aviation terminology came from anyway.  The Brandis was a backup, but it was still as good as it ever was.  It's just that there were newer, better devices available by the time of the flight.

[Chris Owens]

Let me try re-phrasing my question: why did Fred call his marine sextant a "preventer"?

Mona

A somewhat archaic use of the word "preventer", taken from nautical usage, is a secondary or backup item (Webster-dictionary.net 3rd definition)  If we buy that usage, then his marine sextant was a secondary or backup item to have on hand in case his primary sextant failed him.

[Mona Kendrick]

Ah, so it's a nautical term.  Thank you both.

Mona

[Gary LaPook]

Ah, so it's a nautical term.  Thank you both.

Mona

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The most common use of the term "preventer" at sea today is a reference to a line led forward  from the boom when sailing before the wind, with the boom let out all the way to one side, to prevent accidental gybes (due to a sudden change in the wind direction)which would cause the boom to swing all the way around to the other side, possibly knocking someone's head off along the way and/or damaging the  boom or rig.

gl

[Gary LaPook]

Ah, so it's a nautical term.  Thank you both.

Mona

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The most common use of the term "preventer" at sea today is a reference to a line led forward  from the boom when sailing before the wind, with the boom let out all the way to one side, to prevent accidental gybes (due to a sudden change in the wind direction)which would cause the boom to swing all the way around to the other side, possibly knocking someone's head off along the way and/or damaging the  boom or rig.

gl

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"PREVENTER

Any rope used as an additional security for another. A preventer backstay, for example, supplements a backstay."

A Visual Encyclopedia of Nautical Terms Under Sail.  Crown Publishers, New York.